Previous studies of the efficacy of light therapy for winter seasonal affective disorder (SAD) have utilized light boxes, which, though effective and safe, are cumbersome and, at times, inconvenient. A head-mounted, portable light delivery system has been invented and developed by researchers in the Intramural Program of the NIMH and at Jefferson Medical College in an attempt to find a more convenient light treatment source. This past winter, we participated in the third multicenter clinical trial of this device in as many years. The latest study was not performed as part of a CRADA with Bio-Brite, Inc. of Bethesda, MD, the manufacturer of the visor, though the company did provide the visors without charge. In the two earlier studies, we found no difference between visors of widely varying intensities (from 60 to 5000 lux). Although all treatments appeared to be fairly effective, the question remained as to whether this effect was due solely to the placebo effect or to specific effects as well. To address this question, we undertook a third study, in which a very dim (30 lux) red visor, which we predicted would function only as a placebo, was compared to a somewhat brighter (600 lux) white visor in a parallel design in 57 patients with SAD from 2 centers (NIMH, Bethesda, MD and McLean Hospital, Belmont, MA) were assigned randomly to treatments with either a 30-lux red visor or a 600-lux white visor. Treatments were administered for 30 minutes each morning for 2 weeks. The overall response rate for both visors, using stringent response criteria, was approximately 40%. Thus, our prediction that the dimmer visor would be more effective than the brighter one was not confirmed. Possible explanations for this finding are discussed.